#include <iostream>

using namespace std;

int main(){

    double x;
    cin>>x;

    double l =-100,r = 100;
    while(r-l>1e-8){

        double mid = (r+l)/2;
        if(mid*mid*mid >=x) r = mid;
        else l = mid;
    }
    printf("%.6lf\n",l);
    
    return 0;
}